Strain insulator



P 1934- A. o. AUSTIN 1,972,615

STRAIN INSULATOR Filed Jan. 19, 1931 2 Sheets-Sheet l Figl. 7

A TTORNEY Sept. 4, 1934.

A. O. AUSTIN STRAIN INSULATOR Filed Jan. 19, 1931 2 Sheets-Sheet 2IVVENTO R Arf/wr 0. 1403/ A TTORNEY Patented Sept. 4, 1934 PATENT OFFICESTRAIN I NSULATOR Arthur 0. Austin, near Barberton, Ohio, assignor, bymesne assignments, to The Ohio Brass Company, Mansfield, Ohi Jersey 0, acorporation of New Application January 19, 1931, Serial No. 509,643

13 Claims.

3 This invention relates to insulators of wood or other material havingfittings for securing the same to connected parts, and has for one ofits objects the provision of a fitting for gripping a l wood member in amanner to utilize the ultimate strength of the wood and to provide forvariations in size of the member gripped.

A further object is to provide a fitting for strain members which shallbe simple and economical' to manufacture and which shall be efilcient inoperation.

Other objects and advantages will appear from the following description.

The invention is exemplified by the combination and arrangement of partsshown in the accompanying drawings and described in the followingspecification, and it is more particularly pointed out in the appendedclaims.

In the drawings:

Fig. 1 is an elevation of one end of a strain insulator having oneembodiment of the present invention applied thereto.

. Fig. 2 is a section on line 2-2 of Fig. 1. Fig. 3 is an elevation ofone. end of a modified 26 construction.

Fig. 4 is a section on line 4-4 of Fig. 3.

Fig. 5 is a plan of the device shown in Fig. 3.

Fig.6 is a view similar to Fig. 4 but showing a modified arrangement.

Fig. '7 is a view similar to Fig. 1 but showing a different form of theinvention.

Fig. 8 is a plan and Fig. 9 an elevation of one end of a straininsulator having a form of the invention applied thereto.

'Fig. 10 is a view similarto Fig. 3 showing a modified form of theinvention. Fig. 11 is a section on line 11-11 of Fig. 10.

Fig. 12 is a view similar to Fig. 3 showing another modification.

Fig. '13 is a section on line 1313 of Fig. 12.

In high voltage transmission lines where the supporting structures aremade of wood, it is frequently very desirable to make effective use ofthe insulation provided by the wood for high voltage 45 transients, suchasv those produced by lightning or switching. The insulation provided bythe wood is also effective in preventing flashover and line interruptiondue to fog or other severe conditions.

Owing to the limited mechanical strength of wood structures, it iscommon practice to guy structures to increase their mechanical strength.In order to develop the efiective insulation of the structure, however,it is necessary that insulation 55 be placed in the. guys. One method ofproviding insulation in the guys is to use wood tension members of thedesired mechanical and electrical characteristics. It is more or lessdiflicult, however, to provide the necessary reliability in woodmembers, particularly where they are subjected to high stresses intension.

The shrinkage of the wood or its change in volume, due to atmosphericconditions, may destroy the grip of attachments and the mechanicalstrength of the member. When the wood member becomes wet, it tends toexpand and upon drying a fitting which had previously been tight may beloose. In order to provide an attachment which will insure a high degreeof mechanical strength and reliability over a long period of time, it isnecessary and advisable that some means be provided so that thenecessary grip may be maintained even though the thickness or volume ofthe wood member may change. It is also desirable to provide a gripmember for the wood such that any swelling on the part of the wood willtend to be compensated for by the grip member, in order to preventdestruction of the fibres in the wood.

In the form of the invention shown in Fig. 1 a wood or other member 10is provided with a gripping mechanism having an attachment bale or eye11 for connection to a guy or supporting structure. The wood member isprovided with a tapered head 12 fitted with hearing plates 13. Thebearing plates may be extended so as to form horns 14 or the members 14may be separate members if so desired. Tilting grips or toggles 15 areused to transfer the tension from the bale 11 and are so proportionedthat they set up the necessary pressure between the hearing plates 13and the wood and so that the desired strength and tension will beobtained partly through reaction of the members 12 and 13 against eachother and partly through friction produced by the pressure between theplates 13 and the head 12. The tilting grips 15 are held in place by abolt 16 which passes through an oblong opening in the head 12 of thewood member.

A friction plate 17 may be placed in a slot 18 in the head 12 tosupplement the holding action of the plates 13, and where this is done,the bolt 16 fits tightly in an opening through the friction plate 1'7.When a load is applied to the bale 11, it tends to move the grip leverslongitudinally of the member 10. This movement is arrested by the bolt16 and the pressure and friction between the bearing plates 13 and thehead 12. The points of bearing between the bale 11 and the tiltingmembers is such that the inner ends of the tilting members 15 pressagainst the bearing plate 13; the combination producing a lever actionwith the heads of the bolt 16 providing fulcrum abutments. By properlyproportioning the two arms of the levers 15, it is possible to producethe desired pressure for any given tension. 9

By reference to Fig. 1, it is readily seen that should the wood or headmember 12 shrink, the looseness will be readily taken up by the lever ortoggle action. It is also seen that if the pressure increases, due toswelling of the wood, the ends of the toggle member will be thrownoutwardly. The pressure necessary to set up a given frictional load maybe readily regulated by the use of friction plates 1'7, disclosed in myprior Patent Number 1,497,319. The connection between the bale 11 andthe friction plate 17 is usually through the bolt 16,- although ifdesired the friction plates may be attached in other ways, such as tothe bearing plates 13 outside of the wood member. It of course is notnecessary that the bolt 16 pass through the wood as this may be placedoutside of the wood member if desired, or any suitable arrangement maybe used which will provide the necessary tension on the plate 17. Ifdesired the shear on the bolt 16 may be eliminated by allowing the griplevers 15 to bear against projections 19 on the plates 13.

In the form of the invention shown in Figs. 3, 4 and 5 a strap ortension member 21 is placed between tilting grips or toggles 22, 23,and24, clamped together by bolts 25, 26 and 27. These members 22, 23 and 24may bear directly upon the wood strain insulator bar 28 or upon hearingplates 29. Bearing plates 29 may be provided with inclined bearingsurfaces 30. These inclined surfaces may be in the form of ribs pressedout from the plates if so desired. By providing inclined surfaces, it ispossible to obtain more latitude for gripping, as any tendency to slipbetween the members 22, 23 and 24 and the plates by the geometricrelations of the parts so as to provide for a wide range of material.The relation between the ultimate in tension and compression may bequite difierent for various woods or materials used in the tensionmember. By properly designing the toggle action, this variation may beprovided for. If desired, the toggle action may be varied for difierentmembers so that the pressure and grip may be greater in-one member thanin another, in order to prevent the maximum tension or ultimate in thewood member. The bearing plates 29 may be bolted or attached to the woodmember 31 by bolts 32 or other suitable means. While this may not benecessary to secure the necessary ultimate strength of the insulator,looseness and de-arrangement of the parts before tension is applied willbe prevented.

With the arrangement shown, variations in the thickness of the membersmay be readily compensated for by tightening the bolts 25, 26 and 27.This is desirable as the tension members are likely to vary inthickness. If desired,

the wood member may be provided with wedges 33 so as to provide atapered head.

In some cases the gripping members 35 may be made so as to clamp in thedirection of the diagonal of the wood bar 36, as shown in Fig. 6. Thisgives a longer arm from the point of attachment of the bolt 25 to theouter bearing surface of the strap 35 and tends to clamp the wood memberequally from all sides. If desired, a taper. head may be provided bymeans of wedge members 37 which help to provide the necessary tightness.Combined gripping and toggle plates 35. may bear upon bearing plates 38or directly upon the wood itself if so desired. Where the bearing platesrest directly upon the wood, it is usually advisable to round thebearing surfaces so as to prevent crushing of the wood by concentratedpressure due to the tilting of the bearing plates under the toggleaction.

Fig. 7 shows a construction in which a tilting grip or toggle action isproduced by dogs 40 pressing directly upon bearing plates 41. The dogs40 are pivoted at 42 to a bale 43, the arms of which are" held togetherby a yoke 44. The tension member 45 has a taper head 46 engaging thebearing plates 41. The gripping action, as well as compensation forvariations in the parts, is provided by thetilting grip of the dogs 40.

In the modification shown in Figs. 8 and 9, the bale 47 is used inconnection with tilting grips or toggle members 48 and 49 to produce acomponent normal to the axis of the insulating member 50. When tensionis applied to the member 47, a component normal to the axis of themember 50 is produced, owing to the inclination of the portions 51 and52 of the bale 47. The component normal to the member 50 will dependupon the angularity and the tension in the parts 51 and 52. If thetension member 4'! slides easily in the members 48 and 49 and is ratherflexible, the members 48 and 49 may be rigidly connected to hearingplates 53 engaging the faces of the bar 50. In general, however, themembers 48 and 49 may be allowed to tilt or rock upon the bearing plates53. This will not only tend to reduce friction but to produce a furthertightening due to the toggle action. The pressure may be regulated bychanging the angularity of the tension members 51 and 42 relative to aplane through the axis of the insulating bar 50. By making the anglesmall between these members, compression may be reduced so that thecrushing force can be limited.

Forms somewhat similar to that of Fig. 3 are shown in Figs. 10 and 12.The arrangement, however, is such that longer lever arms are ob,- tainedfor the tilting grips. In Fig. 10 the grip or toggle members 55 pressdirectly upon the wood or insulating member 56. This member 56 isprovided with a wedge 57 to provide inclined bearing surfaces and tokeep all of the members tight. Tension bars 60 are disposed between theoverlapping ends of the tilting grips 55 and piv-- oted-to the ends ofthe grips by rivets 58 arranged in spaced lines to provide maximumleverage for the grips 55. In the modification shown in Fig. 12 thewedge 57 is omitted and wedge shaped bearing plates 59 are drivenbetween the contact straps of the tilting grips 55 and the surfaces ofthe wood member 56.

I claim:

1. The combination with a strain member having a flat bearing surface,of a gripper having a flat gripping face engaging said bearing surface,said gripper comprising a rigid lever arm extend- 150 ing transverse tosaid gripping face, a pull member connected to said lever arm fortransmitting a load to said strain member through said gripper, theforce of said load tending to tilt said gripper face, and tie meansholding said gripping face to said bearing surface so that tilting ofsaid gripping face under the force of the load causes said gripper topress against said bearing surface for holding said strain member.

2. The combination with a strain member having flat bearing surfaces atopposite sides thereof, of a pair of grippers having fiat gripping facesengaging said bearing surfaces respectively, said grippers comprisingrigid lever arms extending transverse to said gripping faces, a pullmember connected to said lever arms for transmitting a load to saidstrain member through said grippers, the force of said load tending totilt said gripping faces, and tie means holding said grippers to saidstrain member so that tilting of said gripping faces causes saidgrippers to clamp said strain member.

3. The combination with a strain member, of bearing plates having flatbearing surfaces disposed at opposite sides of said strain member, apair of grippers having fiat gripping faces engaging said bearingsurfaces respectively, said grippers comprising rigid lever armsextending transverse to said gripping faces, a pull member connected tosaid lever arms fortransmitting a load to said strain member throughsaid grippers, the force of the load tending to tilt said grippingfaces, and tie means holding said grippers together so that tilting ofsaid gripping faces causes said grippers to press upon said bearingplates and grip said strain member.

4. The combination with a strain member having relatively inclined, flatbearing surfaces at opposite sides thereof, of a pair of grippers havingflat gripping faces engaging said bearing surfaces respectively, saidgrippers comprising rigid lever arms extending transverse to saidgripping faces, a pull member connected to said lever arms fortransmitting a load to said strain mem ber through said grippers, theforce of said load tending to tilt said gripping faces, and tie meansholding said grippers together so that tilting of said gripping facescauses said grippers to clamp said strain member. 5. The combinationwith a strain member having bearing faces at opposite sides thereof, ofa pair of grippers having gripping faces extending along said bearingfaces in contact therewith, said grippers comprising lever arms rigidtherewith and extending transverse to said gripping faces, a pull memberconnected to said lever arms for transmitting a load to said strainmember through said grippers, and tie means for holding said gripperstogether so that tilting of said gripping faces tends to move portionsof said faces into closer contact with said bearing surfaces.

6. The combination with a strain member having bearing surfaces atopposite sides thereof extending longitudinally of said strain member,of a pair of grippers having gripping faces engaging said bearingsurfaces respectively, said grippers comprising lever arms extendingtransverse to said gripping faces, a pull member connected to said leverarms for transmitting a load through said grippers to said strainmember, the force of said load acting to tilt said gripping facesrelative to said bearing surfaces about contact points of said grippingfaces on said bearing surfaces, and tie means for holding said gripperstogether so that tilting of said gripping faces causes said grippers toclamp said strain member.

'7. The combination with a strain member, of

a pull member therefor, a plurality of grippers for connecting said pullmember with said strain member, and tie means for holding said grippersin cooperative relation with said strain member, said grippers beingdistributed along said strain member and being connected differently onefrom the other to said pull member to exert a. graded gripping force onsaid strain member and thus distribute the load transmitted by saidgrippers to said strain member.

8. The combination with a strain member having bearing surfaces atopposite sides thereof, of a plurality of grippers having gripping facesengaging said bearing surfaces respectively, said grippers comprisinglever arms extending transverse to said gripping faces, a pull memberconnected to said lever arms for transmitting a load to said strainmember through said grippers, the force of said load tending to tiltsaid gripping faces relative to said bearing surfaces about contactlines between said bearing faces and gripping surfaces, and tie meansfor holding said grippers to said strain member, said pull member beingconnected to said grippers at relatively different points on theirrespective lever arms to produce a graded distribution of the grippingaction on said strain member under the force of the load exerted by saidpull member.

9. The combination with a strain member, of U shaped grippers engagingopposite faces of said strain member and a pull member secured to theadjacent legs of said grippers for transmitting a load to said strainmember through said grippers, the force of said load acting to produce atilting moment of said U shaped grippers to cause said grippers to clampsaid strain member.

10. The combination with a strain member, of U straps engaging oppositefaces of said strain member, the legs of said straps extending adjacentthe edges of said strain member, a holding member attached to said legsand exerting a force thereon under the tension of the load on saidstrain member to tilt said straps and cause them to exert a grippingforce on said strain member in proportion to the force of the loadthereon.

11. The combination with a strain member having a flat bearing face, ofa pull member for exerting a load on said strain member, and a tiltinggripper for transmitting said load from said pull member to said strainmember, said tilting gripper being pivoted to one of said members andhaving a flat bearing face engaging the bearing surface of said strainmember, and means for holding said gripper in cooperative relation withsaid strain member, the moment exerted by the load on said gripper beingopposed by the resistance to pressure offered by said strain memberpermitting said gripper to yield to lateral expansion and contraction ofsaid strain member under the restraint of the force of the load on saidgripper.

12. The combination with a strain member, of a pair of grippers havingpivotal engagement with opposite faces of said strain member and havinglinks extending toward each other from said points of pivotalengagement, and a pull member for transmitting a load to said strainmember through said grippers, said pull member being attached toadjacent ends of said links and operating under the force of the loadfor drawing said links inwardly to cause said grippers to clamp saidstrain member.

on said pull member to draw said grippers inwardly, the gripping facesof said rippers having contact portions which are pressed inwardlyagainst the surfaces of said strain member by the tilting movement ofsaid lever arms.

ARTHUR O. AUSTIN.

